1. The Field of the Invention
The present invention relates generally to the interface between physical/electrical media connectors and a communications card in a computer system. More specifically the present invention relates to an improvement in the electrical connection therebetween.
2. The Relevant Technology
The field of transmission of data by phone lines or network cables is a rapidly expanding field. Users of personal computers in particular are finding such practice to be of great value. For example, there are numerous public and private networks and databases which store data or programs. Absent the ability to send and receive data over telephone lines through a modem, a user is relegated to relying upon the exchange of discs or tapes in order to receive data suitable for use with their computer.
Similarly, companies performing tasks that are integrated are aided by local area networks ("LANs") which permit personnel to exchange electronically retrievable data. The ability to freely transfer data and information from one computer to another computer over a telephone or network line may dramatically increase productivity and reduce overall production time.
To translate the binary code utilized by a computer into signals capable of being transmitted over the telephone or network lines, modems have been developed to translate and reconfigure binary signals into analog signals capable of propagation over telephone or network lines. For conversion of signals to take place, a modem must be placed between the computer generating the binary signals and the communication line capable of carrying the analog signals.
Typically, in today's practice, a modem at the transmitting computer end of a communication line receives binary digital data from the computer and converts the binary code received from the computer into modem frequency signals. These modem frequency signals are then transmitted over the communication lines to a receiving modem at the receiving computer.
The modem at the recipient's end then converts the modem frequency signal back to binary digital data characters and inputs the data characters to the input port of the receiving computer.
As today's modems serve to provide a compatible interface between the communication lines and the computer, the Federal Communications Commission ("FCC") and telephone companies require an interface to moderate all signals or energy being input into the phone lines. This interface protects the phone lines and systems from damage, thereby ensuring the integrity and quality of transmissions over the phone lines.
A required part of this interface is a Data Access Arrangement ("DAA") circuit. The DAA circuit provides an impedance match and also serves to isolate the modem and the computer from transient signals and other disturbances coming in over the phone line. The DAA also protects the phone line from disabling influences emanating from the computer or the modem.
For example, damage would occur to the telephone system if instead of transmitting frequency signals, DC power was transmitted over the phone lines. Because the modem is attached directly to the phone line, the modem must incorporate the required FCC interface and must comply with any requirements imposed by local telephone companies.
The ubiquity of the telephone and the need for interactive systems throughout the world have caused standards to be established for the components of a telephonic system. Standardization allows telephone systems and devices using those systems to be interchangeable. The components of the telephone that are most thoroughly standardized are physical/electrical media connectors.
Physical/electrical media connectors are used by almost all telephone and communication companies throughout the world for many applications, the most important of which are interconnection of telephones with telephone lines and networks with network lines. For this reason, stringent standardization of connectors is required if compatibility and interactivity is to be realized.
One popular physical/electrical media connector used in the United States of America is the RJ-11 6-position miniature modular plug physical/electrical media connector. The RJ-11 is used between the telephone line and the telephone itself. Another important standard is the RJ-45 8-position miniature modular plug physical/electrical media connector. The RJ-45 is used primarily for network connectivity.
In contradistinction to the development of telephone lines, transmission or communication lines used in LANs have been developed specifically for the transmission of computer generated signals. Because of the recent development of these transmission lines, a variety of internal configurations for transmission lines have been developed to accomplish the transmission of computer data between computers.
A typical local area network comprises several computers at remote locations throughout a building interconnected with shielded and unshielded twisted pair cable utilizing RJ-type physical/electrical media connectors. The network is typically connected to a file server. A file server is a computer providing shared access to a file system, printer, electronic mail service, or modem. The file server is a combination of hardware and software that contains files shared by everyone connected to the LAN.
As LANs utilizing shielded and unshielded twisted pair cable are capable of transmitting signals at a higher rate than signals traveling through telephone lines, the requirements of the devices used to translate and reconfigure signals from the computer for transmission through lines have consequently been developed with different requirements.
The counterpart to the modem in telephonic communications is the LAN adapter card or data communications card. In a similar fashion to a modem, these communications cards reconfigure the parallel data produced by the computer into a serial form and back. These cards also provide buffering, encoding and decoding, cable access, and transmission.
As the use of LANs increases, it has become increasingly more beneficial for users of portable computers to have the ability to interact with several local area networks at different locations. For example, information at one location may be downloaded to a portable computer that allows a user to manipulate the data during a business trip and load the manipulated data onto the network at a destination. Diagnostics and maintenance are also made easier through the use of common connectors.
As the popularity of twisted-pair cable has increased, the popularity of the most frequently used physical/electrical media connector, the RJ-45 8-pin miniature modular plug, has also increased. This increase in popularity of the 8-pin miniature modular plug has introduced the same problems and solutions into LANs as will be discussed regarding the RJ-11 physical/electrical media connector in the development of modems.
Many modems in use today are configured as external accessory units, housed in their own cases, and attached to the computer. Typically, external modems are electrically connected to the telephone with a telephone extension line utilizing physical/electrical media connectors at each end. External modems are often employed by users of personal computers because they can easily contain a substantial amount of electronic circuitry or hardware, as well as executable programs or software.
With the advent of downsizing technology in computer components, however, smaller portable computers (often referred to as laptop or notebook computers) have taken the place of many of the desktop models which use external modems. With the new-found portability available with laptop or notebook computers, the size of external modems has proved cumbersome and been rendered obsolete in keeping with the portability that buyers of these downsized computers desire.
To overcome the inconvenience and physical limitations of external modems, smaller modems have been developed that are small enough to be built integrally within the housing of a portable computer. As a result, integral internal modems that interface with the ubiquitous RJ-11 and RJ-45 system provides users of portable computers with internal modems having a uniform standard interface for media access devices such as modems. Now, modem manufacturers can build products capable of accepting the RJ-11 and RJ-45 media connectors with confidence that their product can be used in a wide geographical area. Because modems can be built to the RJ-11 and RJ-45 uniform standards, consumers benefit from the ability to interchange and interconnect media access devices without the need for adapters for products made by different manufacturers.
As computer housings have continued to be downsized, internal spatial restrictions have required the establishment of standards for the internal accessories of the computer. One set of standards applicable to memory cards has been developed by the Personal Computer Memory Card International Association (PCMCIA). This organization is comprised of hundreds of manufacturers of memory cards and related peripheral equipment. By convention, the PCMCIA has determined that the spatial standard for all memory cards used in down-sized computers should be restricted to a rectangular space approximately 55 mm in width, 85 mm in length, and 5 mm in depth.
In keeping with the PCMCIA standards for memory cards, internal modem manufacturers have adopted the same spatial standards for use with their down-sized communications cards. By complying with the standards established by PCMCIA for memory cards, communications card manufacturers have assured themselves of compatibility and spatial conformity with computers utilizing the new PCMCIA standards.
The constraints imposed by this new PCMCIA standard have resulted in the development of "credit card" communications cards. Most of the components formerly housed within a modem are now contained within a credit card-sized device. Although many of the communication cards serve the functions of a modem, a similar card has been contemplated for use in LANs. Nonetheless, the problem will hereinafter be addressed in terms of the PCMCIA standard communications card.
Since the depth of a PCMCIA standard communications card is limited to 5 mm and the depth of a typical media connector, such as the RJ-11 type or 8-pin miniature modular plug, is approximately 8-12 mm, the typical media connector exceeds the depth restrictions imposed by the PCMCIA standards for internal computer components.
While many prior art devices have tried to solve the depth incompatibility problem between the PCMCIA standard communications card and the media connector, a "pop-out" or sliding interface device has emerged as a popular solution. The pop-out interface device, known commonly as the XJACK.RTM. initially produced by MEGAHERTZ Corp., now owned by 3 Com Corp., solves many of the interface problems posed by prior art devices. Such solved problems include, but are not limited to: (i) the elimination of carrying along an extra interfacing device compatible with both the media connector and the PCMCIA communications card; (ii) the elimination of ensuring a DAA in the interfacing device is compatible with the computer; (iii) the elimination of physical interference between adjacent PCMCIA communication cards in adjacent slots when the PCMCIA communication card has an enlarged portion thereof larger than the conventional 5 mm thickness; (iv) the elimination of potential breakage of the interface connector when not in use; and (v) the elimination of protrusions beyond the normal dimensions of the computer so that the computer portfolio is more compatible with devices typically transporting laptop computers.
With reference to FIG. 1, a typical embodiment of a sliding interface device in the form of a conventional 5 mm thick PCMCIA-architecture style communications card for directly interfacing with a media connector is depicted generally as 20. The communications card 29 defining the interface device 20 has a retractable access portion 22 and a fixed portion 24.
The fixed portion 24 is in electrical communication with a computer (not shown) by means of electronic circuitry connected on a printed circuit board (PCB) housed internally within the communications card 29. For brevity, fixed portion 24 may sometimes be referred to as the PCB 24 although the fixed portion includes more than just the PCB and electronic circuitry. The retractable access portion 22 is in electrical communication with the fixed portion 24 through a flexible printed circuit board 30. During use, in means well known in the art, the retractable access portion 22 slides in and out of a slot 32 formed within the PCB 24. The retractable access portion 22 is urged out of the slot 32 by a spring 34 biased, in a direction external to the computer housing, by a ledge 36 connected to the PCB 24. Although not shown, the computer housing during use is substantially parallel to an edge 37 of the communications card 29. A limiting notch 42 engaged by a biased lever 40 is used to restrict the travel distance of the interface device to a predetermined distance when the retractable access portion is urged in a direction external to the computer housing by the spring 34. After use, a retention notch 38 in combination with the biased lever 40 is used to retain the retractable access portion 22 within the housing of the computer.
An aperture 44 having a plurality of walls 46 is formed within the retractable access portion 22. The aperture 44 is so sized and shaped as to be capable of receiving a physical/electrical media connector. Formed within aperture 44 by means of walls 46 is a broad retention clip groove 48, a narrow retention clip groove 50, and a retention ridge 52. These structures within aperture 44 provide for the retention of a connector pin block of a physical/electrical media connector. A guide track 54 is formed within communications card 29 protruding upwardly from the bottom of communications card 29. Guide track 54 is interengaged with a corresponding guide groove formed in the bottom of retractable access portion 22.
When a user desires to connect a telephone line to the communications card, biased lever 40 is manipulated out of retention notch 38. As retractable access portion 22 is released from the grip of biased lever 40, tension applied by spring 34 urges retractable access portion 22 out of slot 32. The progress of retractable access portion 22 is guided by guide track 54 and is halted when biased lever 40 engages limiting notch 42. A user then inserts a physical/electrical media connector into aperture 44 to provide an electrical connection between communications card 29 and the telephone line. When a user no longer desires to access the retractable access portion 22, the user merely presses retractable access portion 22 back within the confines of the computer housing until the retention notch 38 is engaged by biased lever 40.
Although extremely effective as a device suitable for physically and electrically interfacing a PCMCIA communications card and a media connector, the sliding interface connectors are limited by certain inherent constraints. For example, the retractable access portion 22 is typically manufactured out of a dielectric material such as a plastic that inherently provides electrical insulation between the media connector and the communication card 29. As media connectors tend to transmit higher rate data, media connectors are increasingly more reliant upon the shielding properties available through the use of shielded cables that are terminated by media connectors. Shielded media connectors typically are comprised of a traditional media connector augmented by a peripheral shielding jacket physically located about the external portion of the media connector and, additionally, electrically coupled to the shielding conductor of the shielded media cable. As those familiar with the art of shielding appreciate, effective shielding requires an electrically conductive path from the cable shielding to a reference ground point. Since prior art attempts do not facilitate the electrical connection of the shield associated with the shielded cable to a common ground reference point, the prior art implementations do not facilitate the available benefits of employing the properties of shielded communication channels.
Accordingly, it would be an advance to provide an improved electrical connection between the media connector and the communications card that accommodates the substantial benefits of shielded cable designs.